System and method for automatic discovery of topology in an LTE/SAE network

ABSTRACT

A system, method and computer program product are disclosed for monitoring a telecommunications network that comprises a plurality of Mobility Management Entity (MME) nodes and a plurality of evolved UTRAN NodeB (eNodeB) nodes coupled by S1-MME interfaces. A Stream Control Transmission Protocol (SCTP) association identifier is assigned to an SCTP association between interconnected MME and eNodeB nodes. Specific S1-MME messages allow discovering the MME nodes and the eNodeB nodes with their network identifiers, identifying the connections between them and populating proper tables for this topology information.

TECHNICAL FIELD

Embodiments are directed, in general, to identifying network nodes andinterfaces in a telecommunications network and, more specifically, toidentifying evolved UTRAN NodeBs (eNodeB) and Mobility Management Entity(MME) nodes and S1-MME interfaces in a Long Term Evolution (LTE)/SystemArchitecture Evolution (SAE) network.

BACKGROUND

In telecommunications networks, such as LTE/SAE networks, new nodes andlinks between nodes are added often as the network grows or is updated.In an LTE/SAE network, MME nodes and eNodeBs may be added to increasethe network coverage area and number of subscribers supported, forexample. New S1-MME links may be added between these nodes. Serviceproviders and network operators typically monitor their network toevaluate operating conditions and to identify and correct networkproblems. A monitoring system used for this purpose needs to know theup-to-date network topology under test, including the new monitorednodes and links, in order to provide correct and accurate measurementsand in addition to correlate the measurements to nodes and links (e.g.correlate the alarms to the network entity affected by such event).

The network topology used by the network monitoring system may beupdated manually by entering each new node and all associated newinterconnections to other nodes. However, manual configuration of thenetwork topology is not desired because it is labor intensive and errorprone. Additionally, such manual topology updates typically are delayedsome period of time after actual physical updating of the network. Inthe time between a network update and a manual topology update, thenetwork monitoring system will not be able to properly analyze networkprotocols or operation.

SUMMARY

Embodiments of the present invention provide a system and method forautodiscovery of network topology. The network monitoring system, whichcaptures a significant portion of the network packets, may analyze thosepackets and identify new nodes and interconnections. The networkmonitoring system collects information regarding new nodes andinterconnections and automatically updates the network topology when newnetwork elements are identified.

In one embodiment, a system, method or computer program product monitorsa telecommunications network. The network may comprise, for example, aplurality of MME nodes and a plurality of eNodeB nodes. The MME nodesand eNodeB nodes are coupled by S1-MME interfaces. A Stream ControlTransmission Protocol (SCTP) association identifier is assigned to anSCTP association between interconnected MME and eNodeB nodes. Anexemplary process for assigning SCTP associations to interconnectednetwork nodes is disclosed in U.S. Patent Application Publication No. US2009/0129267 A1, assigned application Ser. No. 12/096,556, and titled“System and Method for Discovering SCTP Associations in a Network,” thedisclosure of which is incorporated by reference herein in its entirety.An S1-MME message is captured from the S1-MME interfaces via amonitoring probe in a network monitoring system. An MMEGI-MMEC key iscreated based on an MME Group Identifier (MMEGI) and an MME Code (MMEC)in the S1-MME message. An SCTP association identifier is assigned to themessage and a Tracking Area Identity (TAI) can be identified in theS1-MME message.

The MME topology table entry corresponds to the MMEGI-MMEC key. ATA-MMEC key is created based upon the TAI and MMEC parameters in theS1-MME message. One or more additional SCTP association identifiers areadded to the list of SCTP association identifiers in the MME topologytable. The one or more additional SCTP association identifiers are froman entry in a TA-MMEC table. The TA-MMEC table entry corresponds to theTA-MMEC key.

The S1-MME message may include a Globally Unique MME Identity (GUMMEI),wherein the MME Group Identifier (MMEGI) and the MME Code (MMEC) arepart of the GUMMEI. A new entry is created in the MME node topologytable, if the MMEGI-MMEC key is not found in the MME node topologytable. The new entry comprises the MMEGI-MMEC key, the TAI, a GUMMEIgroup identifier, and the SCTP association identifier associated withthe S1-MME message. It may require several S1-MME messages to populateall of the fields for the MME node topology table entries because asingle S1-MME message may not include all of the data required tocomplete an entry in the table.

The MME topology table is searched for existing entries that include theSCTP association identifier associated with the S1-MME message. If anexisting entry includes the SCTP association identifier associated withthe S1-MME message, then the existing entry and the new entry aregrouped together in the MME topology table. The existing entry and thenew entry may be grouped together by assigning the same GUMMEI groupidentifier to both entries.

In another embodiment, a system, method or computer program productmonitors the telecommunications network. An S1-MME message is capturedfrom the S1-MME interfaces via the monitoring probe. The S1-MME messagecomprises an S-Temporary Mobile Subscriber Identity (S-TMSI) but not aGUMMEI parameter. An MMEC and Tracking Area Identity (TAI) areidentified in the S1-MME message, and a SCTP association identifier isassociated with the S1-MME message. The MMEC is part of the S-TMSI. ATA-MMEC key is created based upon the TAI and MMEC parameters. The SCTPassociation identifier from the S1-MME message is added to a list ofSCTP association identifiers for an entry in a TA-MMEC table. TheTA-MMEC entry corresponds to the TA-MMEC key. The SCTP associationidentifier from the S1-MME message is also added to a list of SCTPassociation identifiers for an entry in the MME topology table. Theentry in the MME topology table corresponds to the TA-MMEC key. A newentry is created in the TA-MMEC table if no entry in the TA-MMEC tablematches the TA-MMEC key. The new entry includes the SCTP associationidentifier from the S1-MME message.

In another embodiment, an eNodeB global identifier key is identified inthe S1-MME message and an SCTP association identifier is associated withthe S1-MME message. The SCTP association identifier from the S1-MMEmessage is added to a list of SCTP association identifiers for an entryin an eNodeB topology table. The entry in the eNodeB topology tablecorresponds to the eNodeB global identifier key. A new entry is createdin the eNodeB topology table if no entry in the eNodeB topology tablematches the eNodeB global identifier key. The new entry in the eNodeBtopology table comprises the SCTP association identifier associated withthe S1-MME message. The new entry in the eNodeB topology table alsocomprises the eNodeB global identifier key that is part of the monitoredeUTRAN CGI (Cell Global Identifier).

An SCTP association identifier is selected from an MME entry in an MMEtopology table and compared to SCTP association identifiers stored in anentry in the eNodeB topology table. If the selected MME table SCTPassociation identifier matches one of the eNodeB table SCTP associationidentifiers, then a new entry is added to an MME-eNodeB links table. TheMME-eNodeB links table entry comprising an MME identifier, an eNodeBidentifier, and the matching SCTP association identifier. The MMEidentifier typically comprises the MMEGI, the MMEC, and a GloballyUnique MME Identity GUMMEI; and the eNodeB identifier comprises aneNodeB global identifier.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the system and method in general terms, referencewill now be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

FIG. 1 is a high level schematic diagram of LTE/SAE network;

FIG. 2 illustrates an exemplary embodiment of an MME table;

FIG. 3 illustrates an exemplary embodiment of a TA-MMEC table;

FIG. 4 illustrates the relationship between the MME table and theTA-MMEC table;

FIG. 5 illustrates an exemplary embodiment of an eNB table used in theeNodeB discovery;

FIG. 6 illustrates an exemplary embodiment of an MME-eNodeB links tablefor linking the MMEs and eNodeBs;

FIG. 7 is a high level example of one embodiment of a state machine fordiscovering MME and eNodeB nodes and binding to them the correspondingSCTP associations;

FIG. 8 is a flowchart for an exemplary MME node discovery process;

FIG. 9 is a flowchart for an exemplary process for evaluating multipleGUMMEI;

FIG. 10 is a flowchart for fan exemplary process for identifying MMEnodes;

FIG. 11 is a flowchart for an exemplary process for discovering eNodeBtopology; and

FIG. 12 is a flowchart for an exemplary process for link creation.

DETAILED DESCRIPTION

FIG. 1 is a high level schematic diagram of LTE/SAE network 100. In aLTE/SAE network, the S1 interface is an interface between an evolvedUniversal Terrestrial Radio Access Network (eUTRAN) and core networknodes. The S1 interface may be designated as a control plane interface(S1-MME) or a user plane interface (S1-U). In exemplary network 100,eNodeBs 101 and 102 in the eUTRAN are coupled to MMEs 103 and 104 in thecore network by S1-MME interfaces 21-24.

MMEs 103 and 104 are the signaling nodes interfacing the eNodeBs on oneside and the rest of the packet core network on the other side. The corenetwork is designated as an Evolved Packet Core (EPC) in LTE/SAE. TheMMEs are responsible for Non-Access Stratum (NAS) signaling to the userequipment (UE), for mobility handling either inter-MME or inter-RAT(inter-Radio Access Technologies, e.g. UTRAN/GERAN), for initiatingpaging and authentication of user equipment (UE), for establishing thetraffic bearers on the S1 side and on the EPC side as well. The MMEsmaintain location information as the list of Tracking Areas where eachuser can be located. Multiple MMEs can be grouped together in an MMEpool to meet the signaling load in the network.

The eNodeBs are enhanced NodeBs that provide the air interface andperform radio resource management in LTE/SAE network 100. Each eNodeBmay be coupled to multiple MMEs. Similarly, each MME may be coupled tomultiple eNodeBs. Stream Control Transmission Protocol (SCTP) is thetransport layer protocol for S1 interface control plane signaling onS1-MME interfaces 21-24. Between a specific pair of eNodeB-MME nodes,there will be only one SCTP association, even if there are multiple IPaddresses at either or both node. An SCTP Association Identifieridentifies the SCTP association between the two nodes. This parametercan be used to globally identify a specific SCTP association.Embodiments of the present invention correlated each SCTP association tothe specific MME and eNodeB nodes to which it refers. An exemplaryprocess for correlating SCTP associations to interconnected networknodes is disclosed in U.S. Patent Application Publication No. US2009/0129267 A1, assigned application Ser. No. 12/096,556, and titled“System and Method for Discovering SCTP Associations in a Network,” thedisclosure of which is incorporated by reference herein in its entirety.

Messages exchanged on the control plane interface (S1-MME) are used, forexample, to set up calls for the UE. Once the calls are set up, userplane packets are sent from eNodeBs 101 and 102 over the user planeinterfaces (S1-U) 25-26 to Serving Gateway (S-GW) 105, which routes andforwards the packets.

During network access, the serving MME allocates a Globally UniqueTemporary Identity (GUTI) to the UE. The use of the GUTI avoids theexchange of a UE's permanent identity (International Mobile SubscriberIdentity—IMSI) over the radio access link. The GUTI consists of twocomponents: a Globally Unique MME Identity (GUMMEI) and an MME TemporaryMobile Subscriber Identity (M-TMSI). The GUMMEI is the identity of theMME that has allocated the GUTI. The M-TMSI is the identity of the UEwithin that MME.

The GUMMEI consists of the Public Land Mobile Network (PLMN) Identifierand the MME Identifier (MMEI). The PLMN Identifier consists of theMobile Country Code (MCC) and Mobile Network Code (MNC). The MMEIconsists of the MME Group Identifier (MMEGI) and the MME Code (MMEC).The MMEC provides a unique identity to an MME within the MME pool, whilethe MMEGI is used to distinguish between different MME pools within thenetwork.

Geographical areas served by the MME pool are designated as TrackingAreas (TA). UEs are located within the TAs, which may be served by oneor more MMEs in the pool. The 3GPP specifications define an MME poolarea as an area within which a UE may be served without having to changethe serving MME. An MME pool area is served by one or more MMEs (i.e. apool of MMEs) in parallel. The MME pool areas are a collection ofcomplete Tracking Areas, and the MME pool areas may overlap each other.The network operator must ensure that the MMEC is unique within the MMEpool area and, if overlapping pool areas are used, the MMEC must beunique within the area of overlapping MME pools.

Based upon these requirements, it is possible to build a relationbetween

MME pool areas and tracking areas. The following conclusions can bedrawn: The MMEC code is unique per MME pool area; the MMEC code isunique within areas of overlapping MME pools; and an MME pool area is acollection of complete TAs. Accordingly, a specific MMEC code is uniqueper TA. Two MME nodes cannot have the same MMEC code serving the sameTA. This rationale is one of the bases for the MME auto-discoveryalgorithm described herein.

Individual eNodeBs may be designated with a name or other identifier(eNB NAME). Additionally, a global identifier is assigned to each eNodeB(eNB Global ID), which contains the PLMN identity and the eNodeBidentity used within the PLMN. An eNodeB can serve one or more cells,each one identified by an eUTRAN Cell Global Identifier (eUTRAN CGI).The eUTRAN CGI contains the PLMN identity and a cell identity.

TABLE 1 is a list of parameters that are useful for auto-discovery ofMME and eNodeB topology. TABLE 1 also explains the relationship betweenthe different identifiers. For example, both GUTI and GUMMEI include theglobal MME identifier (MMEGI-MMEC), and the S-TMSI includes the MMECidentifier, but not the MMEGI.

TABLE 1 Parameter name Description MME Pool A set of MMEs that can sharethe load of a number of eNodeBs. The MME pool covers a complete numberof tracking areas. MMEGI MME Group ID Identifies a MME pool globally inthe network. MMEC MME Code Identifies a specific MME in the pool. GUMMEIGlobally Unique MME Identifier = MCC + MNC + MMEGI + MMEC Identifier ofthe MME that is globally unique in all the LTE/SAE mobile networks. MCC= Mobile Country Code MNC = Mobile Network Code GUTI Globally UniqueTemporary Identity = GUMMEI + M-TMSI Globally Unique Identifierallocated by an MME to a UE. S-TMSI S-Temporary Mobile SubscriberIdentity = MMEC + M-TMSI Shortened form of GUTI that is unique onlywithin a certain MME. TAC Tracking Area Code Code identifying ageographical area where the UE can be located. TAI Tracking AreaIdentity Identity of the tracking area in the form: MCC + MNC + TAC eNBNAME Optional identifier that can be assigned to an eNodeB. eNB GlobalID eNodeB Global Identifier = PLMN identity + eNodeB identity Globalidentifier of the eNodeB. The eNodeB identity is 20 bits long if a“Macro eNodeB” or 28 bits long if a “Home eNodeB.” The Macro eNodeB ishandling normal cells, while the Home eNodeB is a Femto cell itself.e-UTRAN CGI e-UTRAN Cell Global Identifier = PLMN identity + CellIdentity The 20 left-most bits of the “Cell Identity” are the “eNodeBidentity” in case of normal Macro eNodeB. The entire “Cell Identity” (28bits) is the “eNodeB identity” in case of Home eNodeB.

Network monitoring system 106 may be used to monitor the performance ofnetwork 100. Monitoring system 106 captures packets that are transportedacross interfaces 21-26 and any other network links or connections. Inone embodiment, packet capture devices are non-intrusively coupled tonetwork links 21-26 to capture substantially all of the packetstransmitted across the links. Although only links 21-26 are shown inFIG. 1, it will be understood that in an actual network there may bedozens or hundreds or more of physical, logical or virtual connectionsand links between network nodes. In one embodiment, network monitoringsystem 106 is coupled to all or a high percentage of these links. Inother embodiments, network monitoring system 106 may be coupled only toa portion of network 100, such as only to links associated with aparticular service provider. The packet capture devices may be part ofnetwork monitoring system 106, such as a line interface card, or may beseparate components that are remotely coupled to network monitoringsystem 106 from different locations.

Monitoring system 106 preferably comprises one or more processorsrunning one or more software applications that collect, correlate andanalyze media and signaling data packets from network 100. Monitoringsystem 106 may incorporate protocol analyzer, session analyzer, and/ortraffic analyzer functionality that provides OSI (Open SystemsInterconnection) Layer 2 to Layer 7 troubleshooting by characterizingthe traffic by links, nodes, applications and servers on network 100.Such functionality is provided, for example, by the Iris Analyzertoolset available from Tektronix, Inc. The packet capture devicescoupling network monitoring system 106 to links 21-26 may be high-speed,high-density 10GE probes that are optimized to handle high bandwidth IPtraffic, such as the GeoProbe G10 available from Tektronix, Inc. Aservice provider or network operator may access data from monitoringsystem 106 via user interface station 107 having a display or graphicaluser interface 108, such as the IrisView configurable software frameworkthat provides a single, integrated platform for all applications,including feeds to customer experience management systems and operationsupport system (OSS) and business support system (BSS) applications,which is also available from Tektronix, Inc. Monitoring system 106 mayfurther comprise internal or external memory 109 for storing captureddata packets, user session data, call records and configurationinformation. Monitoring system 106 may capture and correlate the packetsassociated specific data sessions on links 21-26. In one embodiment,related packets can be correlated and combined into a record for aparticular flow, session or call on network 100.

Network 100 is continually evolving as additional eNodeBs and MMEs areadded to the network system and as new interconnections are createdeither between new network elements or between new and existing networkelements. To properly analyze the operation of network 100, monitoringsystem 106 needs to know the topology of the network, including theexistence and identify of all network nodes, such as eNodeBs and MMEs,and the interconnections among the network nodes. In a preferredembodiment of the invention, monitoring network 106 detects the presenceof eNodeBs and MMEs and the associated S1-MME interfaces.

The S1-MME interfaces carry S1-AP messages including SCTP TA (transportaddress) pairs and, for specific messages, the Transport Layer Address(TLA) either of the eNodeB or the S-GW to be used on the S1-U interface.The messages monitored over the S1-MME interfaces may be used bymonitoring system 106 for auto-discovery of the MME nodes. The S1Application Protocol (S1-AP) is used to set up UE-associated logical S1connections between an eNodeB and an MME. The S1-AP protocol is used tomanage such connections and also to send UE-related NAS messages overthe S1-MME interface. Other important features of S1-AP concern thesupport of mobility, the management of the eNodeB-MME connection and themanagement of RABs (Radio Access Bearers), with all the messages thatconcern their creation, modification and release.

TABLE 2 lists topology-relevant S1-AP/NAS messages that are monitoredfor MME node discovery according to an exemplary embodiment of theinvention.

TABLE 2 Message Name/ Direction/Layer Relevant parameters in messagefields ATTACH REQUEST “EPS Mobile Identity” in the form of GUTIDirection: eNB → MME (for former MME), present if UE has a validProtocol layer: NAS GUTI, or alternatively, in the form of IMSI Lastvisited registered TAI, present if the UE has a valid TAI to include.Unciphered message TRACKING AREA GUTI (for former MME) UPDATE REQUESTLast visited registered TAI, present if the UE Direction: eNB → MME hasa valid TAI to include. Protocol layer: NAS Unciphered message TRACKINGAREA GUTI (optional, but present when UPDATE ACCEPT reallocated)Direction: MME → eNB TAI list (optional parameter) Protocol layer: NASMessage may be ciphered GUTI REALLOCATION GUTI COMMAND TAI list(optional parameter) Direction: MME → eNB Message may be cipheredProtocol layer: NAS ATTACH ACCEPT GUTI (optional, but present whenDirection: MME → eNB reallocated) Protocol layer: NAS TAI list Messagemay be ciphered DETACH REQUEST GUTI (if UE has a valid GUTI,alternatively, (UE originated) IMSI) Direction: eNB → MME Message may beciphered Protocol layer: NAS PAGING List of Tracking Area Identities(TAI) Direction: MME → eNB UE Paging Identity (S-TMSI, or IMSI if noProtocol layer: S1-AP valid S-TMSI) INITIAL UE MESSAGE Tracking AreaIdentity (TAI) Direction: eNB → MME S-TMSI Protocol layer: S1-AP TheS-TMSI is an optional parameter but, if the eNodeB receives S-TMSI viathe radio interface, it is included in S1-AP. MME CONFIGURATION MME NAME(optional parameter) UPDATE List of GUMMEIs Direction: MME → eNBProtocol layer: S1-AP S1 SETUP RESPONSE MME NAME (optional parameter)Direction: MME → eNB List of GUMMEIs Protocol layer: Sl-AP

The messages in TABLE 2 are useful in embodiments of an auto-discoveryalgorithm. Some messages, such as the ATTACH REQUEST, TRACKING AREAUPDATE REQUEST, PAGING, and INITIAL UE MESSAGE, are more important oruseful than the other messages because they are unciphered and occurquite frequently.

TABLE 3 lists topology-relevant S1-AP messages that are monitored foreNodeB discovery according to an exemplary embodiment of the invention.

TABLE 3 Message Name/ Direction/Layer Relevant parameters in messagefields S1 SETUP REQUEST eNB NAME Direction: eNB → MME eNB Global IDProtocol layer: S1-AP HANDOVER NOTIFY eUTRAN CGI (including eNB GlobalID) Direction: eNB → MME Protocol layer: S1-AP PATH SWITCH eUTRAN CGI(including eNB Global ID) REQUEST Direction: eNB → MME Protocol layer:S1-AP INITIAL UE MESSAGE E-UTRAN CGI (including eNB Global ID)Direction: eNB → MME Protocol layer: S1-AP LOCATION REPORT eUTRAN CGI(including eNB Global ID) Direction: eNB → MME Protocol layer: S1-APUPLINK NAS eUTRAN CGI (including eNB Global ID) TRANSPORT Direction: eNB→ MME Protocol layer: S1-AP CELL TRAFFIC TRACE eUTRAN CGI (including eNBGlobal ID) Direction: eNB → MME Protocol layer: S1-AP

Embodiments of the present invention comprise a topology applicationthat applies an algorithm to determine a network's topology. Thealgorithm uses S1-MME messages and the parameters in those messages todiscover and identify MME nodes and eNodeBs in the network. The basicassumptions for the algorithm are that:

-   -   every protocol data unit (PDU) comes to the topology application        associated together with an SCTP ASSOCIATION ID, which        identifies the SCTP association to which the PDU belongs. The        SCTP association ID is assigned by a separate application that        is focused on the auto-discovery of the SCTP associations; and    -   the NAS protocol may be encrypted.

The S1 node autodiscovery algorithm has the following goals:

-   -   discover the MME nodes as identified by the MMEGI-MMEC values;    -   manage the scenario in which a physical MME node can own        multiple MMEGI-MMEC codes by grouping together all the        identifiers and assigning them to the same unique physical node;    -   discover the eNodeB nodes as identified by the eNodeB Global ID;    -   assign the proper SCTP associations to the discovered nodes.

The algorithm may be embodied as a state machine that receives S1-MMEframes as the input and provides the network topology (i.e. nodes withthe linked SCTP associations) as the output. In one embodiment, the S1node autodiscovery algorithm uses a data model comprising four differenttables, which may be hash tables, for example. The data model tables andtheir contents are used in the state machine. The four tables are:

-   -   MME table    -   TA-MMEC table    -   eNB table    -   MME-eNB link table

FIG. 2 illustrates an exemplary embodiment of an MME table 200. Each row201, 202 of the MME table describes an MME logical node. In somesituations, a single physical MME node may correspond to multiplelogical MME nodes. For example, logical node MMEGI₁-MMEC₁ (201) andMMEGI₁-MMEC_(K) (202) are different logical MME nodes that may reside onthe same physical MME node. The value of the GUMMEI GROUP ID parameter203 will be the same for all of the MME logical nodes that areassociated with the same physical MME node. The GUMMEI GROUP IDidentifier is a system-defined parameter, not a 3GPP protocol parameter.Each logical MME 201, 202 has a list of SCTP associations 204 and a listof tracking areas 205. The SCTP associations 204 are toward the eNodeBs,but MME table 200 does not contain relations to each specific eNodeB.

FIG. 3 illustrates an exemplary embodiment of a TA-MMEC table 300, whichcontains parameters that describe the relation between each TrackingArea (TA) 301 and the MMECs 302 serving the TA. Several MMECs may servethe same TA, as shown in entries in table 300. For example, in entries303 and 304, MMEC₁ and MMEC_(K) both serve TA₁. Each TA-MMEC entry islinked to the SCTP Association IDs 305 of the frames that carried theTA-MMEC information.

FIG. 4 illustrates the relationship between MME table 200 and TA-MMECtable 300. The content of MME table 200 is completed using the contentfrom TA-MMEC table 300 to provide the final topology. The MME andTA-MMEC tables are compiled using two different set of parameters. TheMME entries in table 200 are typically complied without the SCTPAssociation ID values. On the other hand, the TA-MMEC entries in table300 typically include the SCTP Association ID values (305). The entriesin each row of MME table 200 are completed using the content of TA-MMECtable 300 (401). The algorithm can bind together entries from each tableusing the MMEC-TA values that are present in both tables. Once an MMEtable entry is identified as a match in the TA-MMEC table, then the MMEtable entry is completed with the corresponding SCTP Association IDs inthe TA-MMEC table.

FIG. 5 illustrates an exemplary embodiment of an eNB table 500 used inthe eNodeB discovery. The eNodeBs are identified by their Global ID 501.A list of SCTP Association IDs 502 is linked to each Global ID entry.The SCTP associations 502 are toward the MME.

FIG. 6 illustrates an exemplary embodiment of table 600 for linking theMMEs and eNodeBs. MME-eNodeB links table 600 shows the informationcollected for each S1-MME link between an MME and an eNodeB. The linksare identified by the identifiers of the node endpoints 601-604 and theunique SCTP association ID 605. The MME nodes are identified by MMEGI601, MMEC 602 and GUMMEI GROUP ID from Table 200 (FIG. 2), and theeNodeBs are identified by eNB Global ID from Table 500.

As noted above, the S1 node autodiscovery algorithm may be embodied as astate machine. FIG. 7 is a high level example of one embodiment of astate machine 700 for discovering MME and eNodeB nodes and thecorresponding SCTP associations. In State 1 (800), the algorithmdiscovers MME Nodes and moves to one of several other states. In State 2(900), the algorithm checks whether multiple logical MME nodes should begrouped in the same physical MME node and then moves to State 4. InState 3 (1000), the algorithm handles the S-TMSI parameter and completesthe discovery of MME nodes and then moves to State 4. In State 4 (1100),the algorithm discovers eNodeB nodes, and then moves to State 5 (1200)which binds the SCTP Association ID to the nodes. Each of these statesis described in more detail below in connection with FIGS. 8-12.

FIG. 8 is a flowchart for an exemplary MME node discovery process inState 1 800. State 1 is the basic state for MME node discovery.Depending on the parameters present in an S1-MME frame, a new MME may bediscovered directly in this state, or it is moved to another stateeither for handling partial information present in the S-TMSI or foreNodeB discovery. The MME topology is detected based upon an analysis ofthe GUMMEI and S-TMSI values present in captured S1-MME frames. New MMEentries are created in the MME tracking table if the node has notpreviously been detected. After evaluating the S1-MME message for newMME nodes, the frame is forwarded to the state for new eNodeB detection.The processes illustrated in FIGS. 8-12 may be performed, for example,in a network monitoring system, such as network monitoring system 106described above in connection with FIG. 1.

Starting in step 800, the MME node discovery process receives S1-MMEframes in step 801. In step 802, the process evaluates whether a GUMMEIparameter is present in the S1 message. If a GUMMEI parameter is presentin the S1 message, the algorithm completely identifies the MME. In step803, a key comprising MMEGI and MMEC is created from the GUMMEIparameter. Step 803 also gets the SCTP Association ID from the S1-MMEmessage and, if present, the TAI or TAI list. With the informationcollected in step 803, the process moves to step 804 wherein itdetermines if the MMEGI-MMEC key is already present in the MME nodetopology of table 200 (FIG. 2). If the MMEGI-MMEC key is present in thetable, then the associated MME node has already been discovered and theprocess moves to step 806. If the MMEGI-MMEC key is not found in thetable, then the associated MME node is new to the network topology andthe process moves to step 805 to create a new node.

In step 805, a new entry is created in MME table 200 with the MMEGI-MMECkey, the TAI or TAI list (if present), and a new system-defined GUMMEIGROUP ID. If the GUMMEI is not from an “old GUTI” (i.e. the GUTI for theformer MME), then the SCTP Association ID is updated in MME table 200. Anew set of associations are also created in TA-MMEC table 300 (FIG. 3).The process then moves to step 806 in which the fields of MME table 200are populated using, for example, process 400 that is illustrated inFIG. 4. If TAI or TAI list is present in the S1-MME message, then thekey TA-MMEC is created using the MMEC from the GUMMEI. The TA-MMEC table300 is then searched using this key. If the key matches an entry in theTA-MMEC table 300, then the corresponding MMEGI-MMEC entry in MME table200 is updated with the SCTP Association IDs from TA-MMEC table 300. Theprocess then moves to step 807 and the MMEGI-MMEC key and SCTPAssociation IDs are sent to a State 2 process 900 (FIG. 9) to check forthe presence of multiple GUMMEIs that are assigned to the same physicalMME.

If GUMMEI is not present in step 802, then the process moves to step 808to determine if S-TMSI is present in the frame. If the S-TMSI ispresent, then the process moves to step 809, which sends the S-TMSI, TAIlist (if present), and S1-MME frame to State 3 process 1000 (FIG. 10)for S-TMSI handling.

If neither GUMMEI nor S-TMSI are present in the S1 frame in step 808,the process moves to step 810, which sends the S1-MME frame to State 4process 1100 (FIG. 11) for eNodeB discovery.

In State 2, several logical MMEs can refer to the same physical MMEnode. FIG. 9 is a flowchart for an exemplary process for evaluatingmultiple GUMMEI and determining if two logical MMEs need to be grouptogether into the same physical MME node. If two logical MMEs aregrouped together, they are both assigned the same GUMMEI GROUP ID value.All MME node records that refer to the same physical MME node aregrouped together even if different GUMMEI values are used. The SCTPAssociation ID is used to group together the related GUMMEI entries inthe MME table.

Initial step 900 is entered from State 1 (FIG. 8). In step 901,MMEGI-MMEC and SCTP Association IDs are received from State 1, whereMMEGI-MMEC key is associated with a newly discovered MME in State 1. Instep 902, the MME table is checked to determine if there is anotherMMEGI-MMEC entry with the same SCTP association ID. If no other entriesin the MME table have the same SCTP association ID, then the processproceeds to State 4 1100. If other entries in the MME table do have thesame SCTP association ID, then there is a physical MME node in thenetwork that has multiple GUMMEI values assigned to it. In step 903, thetwo MMEGI-MMEC entries with the same SCTP association ID are groupedtogether. These entries may be grouped together by assigning the samesystem-defined code, such as the GUMMEI GROUP ID, to both entries. Theprocess then proceeds to State 4 1100 after grouping related MMEGI-MMECentries.

In State 3, MMEC information from the S-TMSI is processed to completethe discovery of the MME nodes when MMEGI information is not availableto create an MMEGI-MMEC key. FIG. 10 is a flowchart for an exemplaryprocess for identifying MME nodes when GUMMEI information is not presentin the received S1-MME frame processed in State 1. Because the S-TMSIincludes the MMEC parameter—but not the MMEGI—it is possible topartially identify an MME node using the S-TMSI. In State 3, new MMEnodes are not created in the MME table. Instead, an MME record iscreated only with TA, MMEC and SCTP Association ID information in theTA-MMEC table. This record can be resolved with MMEGI received in laterS1 frames.

Initial step 1000 is entered from State 1 (FIG. 8). In step 1001,S-TMSI, TAI list and S1 frame data is received from State 1. In step1002, a TA-MMEC key is created using the MMEC from the S-TMSI capturedfrom the S1-MME frame and TAI from the same S1-MME frame. Then theTA-MMEC table is searched for entries with the same key values. Step1003 determines if there are any entries with the same TA-MMEC key. Ifthere are matching entries in the TA-MMEC table, then, in step 1004,these entries are updated with the SCTP Association ID from the S1frame. If there are no entries in the TA-MMEC table with matchingcriteria in step 1003, then a new record is created in step 1005 withthe TA-MMEC and SCTP Association ID.

In step 1006, the MME table is searched using the TA-MMEC just got fromthe S1-MME frame as a key. If an entry matches this criteria, then thealgorithm updates the SCTP Association ID values in the MME table, ifnot already present, using the entry in the TA-MMEC table. In step 1007,the S1 frame is sent to State 4 1100 for eNB node discovery.

The same S1 frame can be used to discover both MME nodes and eNodeBs. InState 4, eNodeB nodes are discovered and linked to the SCTP AssociationID. The eNodeBs are identified based on the presence of the eUTRAN CGIparameter, which includes the global identifier of the eNodeB—eNodeBGlobal ID. FIG. 11 is a flowchart for an exemplary process fordiscovering eNodeB topology. Initial step 1100 is entered from States 1or 3 (FIGS. 8 and 10). In step 1101, an S1-MME frame is received, and instep 1102, the S1-MME frame is analyzed for the eUTRAN CGI. If no eUTRANCGI is present, then the process returns to State 1 800 where thealgorithm waits for and processes the next S1-MME frame.

If the eUTRAN CGI is present in step 1102, then the process moves tostep 1103 in which the eNB Global ID key is obtained from the eUTRAN CGIparameter and used to search the eNB table 500. In step 1104, theprocess determines whether the eNB Global ID key is present in the eNBtable. If the eNB Global ID key is present, then the process moves tostep 1106. If the eNB Global ID key is not already present in the eNBtable, then, in step 1105, a new eNB entry is created using the eUTRANCGI parameter, which includes the eNB Global ID key. After creating thenew entry, the process moves to step 1106 where the SCTP Association IDlist for the eNB entry is updated. The process then moves to State 51200.

In State 5, the MME and eNodeB topology tables are scanned to bindtogether nodes using the SCTP Association IDs. State 5 identifies linksbetween nodes in the network topology. FIG. 12 is a flowchart for anexemplary process for link creation. In State 5, the algorithm loopsthrough the MME table (step 1201) and the eNodeB table (1203) to bindequal values of the SCTP Association ID parameter found in both tables.In step 1202, the lists of SCTP Association IDs are retrieved for eachMME entry in the MME table. In step 1204, those SCTP Association IDs arecompared to the SCTP Association IDs from the entries in the eNodeBtable to identify matching values. If a match is found, then therelationship: MME-eNodeB-SCTP Association ID is stored in the networktopology to identify new links between nodes. The SCTP Association IDcomparison continues for each entry in the MME and eNodeB tables. Whenall the MME entries and eNodeB entries have been evaluated, the processreturns to State 1 800 to process the next S1 frame.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions,and the associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A method of monitoring a telecommunications network, the networkcomprising a plurality of Mobility Management Entity (MME) nodes and aplurality of evolved UTRAN NodeB (eNodeB) nodes, the MME nodes andeNodeB nodes coupled by S1-MME interfaces, wherein a Stream ControlTransmission Protocol (SCTP) association identifier is assigned to anSCTP association between interconnected MME and eNodeB nodes, the methodcomprising: capturing an S1-MME message from the S1-MME interfaces via amonitoring probe in a network monitoring system; creating an MMEGI-MMECkey comprising an MME Group Identifier (MMEGI) and an MME Code (MMEC) inthe S1-MME message; associating an SCTP association identifier to theS1-MME message; identifying a Tracking Area Identity (TAI) in the S1-MMEmessage; adding the SCTP association identifier from the S1-MME messageto a list of SCTP association identifiers for an entry in an MMEtopology table, wherein the MME topology table entry corresponds to theMMEGI-MMEC key; creating a TA-MMEC key from the TAI and MMEC parametersin the S1-MME message; and adding one or more additional SCTPassociation identifiers to the list of SCTP association identifiers inthe MME topology table, wherein the one or more additional SCTPassociation identifiers are from an entry in a TA-MMEC table, theTA-MMEC table entry corresponding to the TA-MMEC key; and selecting anSCTP association identifier from an MME entry in the MME topology table;comparing the selected MME table SCTP association identifier to SCTPassociation identifiers stored in an entry in an eNodeB topology table;and if the selected MME table SCTP association identifier matches one ofthe eNodeB table SCTP association identifiers, then adding an entry toan MME-eNodeB links table, the MME-eNodeB links table entry comprisingan MME identifier, an eNodeB identifier, and the matching SCTPassociation identifier.
 2. The method of claim 1, wherein the S1-MMEmessage comprises a Globally Unique MME Identity (GUMMEI), and whereinthe MME Group Identifier (MMEGI) and the MME Code (MMEC) are part of theGUMMEI.
 3. The method of claim 2, further comprising: creating a newentry in the MME node topology table, if the MMEGI-MMEC key is not foundin the MME node topology table, wherein the new entry comprises theMMEGI-MMEC key, the TAI, and a GUMMEI group identifier; and wherein thenew entry further comprises SCTP association identifier associated withthe S1-MME message, if the Globally Unique Temporary Identity (GUTI) inthe S1-MME message is for a current MME.
 4. The method of claim 3,further comprising: searching the MME topology table for existingentries that include the SCTP association identifier associated to theS1-MME message; and if an existing entry includes the SCTP associationidentifier from the S1-MME message, then grouping the existing entry andthe new entry together in the MME topology table.
 5. The method of claim4, further comprising: grouping the existing entry and the new entry byassigning a same GUMMEI group identifier to both entries.
 6. The methodof claim 1, wherein the MME identifier comprises the MMEGI, the MMEC,and a Globally Unique MME Identity (GUMMEI); and wherein the eNodeBidentifier comprises an eNodeB global identifier.
 7. A method ofmonitoring a telecommunications network, the network comprising aplurality of Mobility Management Entity (MME) nodes and a plurality ofevolved UTRAN NodeB (eNodeB) nodes, the MME nodes and eNodeB nodescoupled by S1-MME interfaces, wherein a Stream Control TransmissionProtocol (SCTP) association identifier is assigned to an SCTPassociation between interconnected MME and eNodeB nodes, the methodcomprising: capturing an S1-MME message from the S1-MME interfaces via amonitoring probe in a network monitoring system; identifying an MME Code(MMEC) in the S1-MME message; identifying a Tracking Area Identity (TAI)in the S1-MME message; associate an SCTP association identifier to theS1-MME message; creating a TA-MMEC key from the TAI and MMEC parametersin the S1-MME message; adding the SCTP association identifier from theS1-MME message to a list of SCTP association identifiers for an entry ina TA-MMEC table, wherein the TA-MMEC entry corresponds to the TA-MMECkey; and adding the SCTP association identifier from the S1-MME messageto a list of SCTP association identifiers for an entry in an MMEtopology table, wherein the entry in the MME topology table correspondsto the TA-MMEC key; and selecting an SCTP association identifier from anMME entry in the MME topology table; comparing the selected MME tableSCTP association identifier to SCTP association identifiers stored in anentry in an eNodeB topology table; and if the selected MME table SCTPassociation identifier matches one of the eNodeB table SCTP associationidentifiers, then adding an entry to an MME-eNodeB links table, theMME-eNodeB links table entry comprising an MME identifier, an eNodeBidentifier, and the matching SCTP association identifier.
 8. The methodof claim 7, further comprising: determining that a Globally Unique MMEIdentity (GUMMEI) parameter is not present in the captured S1-MMEmessage.
 9. The method of claim 7, wherein the S1-MME message comprisesan S-Temporary Mobile Subscriber Identity (S-TMSI), and wherein the MMECode (MMEC) is part of the S-TMSI.
 10. The method of claim 7, furthercomprising: creating a new entry in the TA-MMEC table if no entry in theTA-MMEC table matches the TA-MMEC key.
 11. The method of claim 10,wherein the new entry comprises the SCTP association identifier from theS1-MME message.
 12. The method of claim 7, further comprising: selectingan SCTP association identifier from an MME entry in the MME topologytable; comparing the selected MME table SCTP association identifier toSCTP association identifiers stored in an entry in an eNodeB topologytable; and if the selected MME table SCTP association identifier matchesone of the eNodeB table SCTP association identifiers, then adding anentry to an MME-eNodeB links table, the MME-eNodeB links table entrycomprising an MME identifier, an eNodeB identifier, and the matchingSCTP association identifier.
 13. The method of claim 12, wherein the MMEidentifier comprises the MMEGI, the MMEC, and a Globally Unique MMEIdentity (GUMMEI); and wherein the eNodeB identifier comprises an eNodeBglobal identifier.